Helium Leak Testing
- The HV Port opens to the vacuum and has the highest sensitivity.
- The Sniffer Port opens to atmosphere and has a lower sensitivity.
Leak Tightness Checked with at Least 2 Configurations
Vacuum Inspection: Tests gas inside a part where the part is inside an expansive vacuum chamber, with vacuum under 0.02 psi absolute or 1 mBar absolute pressure. This known as “hard vacuum.” This is the most sensitive and recommended test method.
Atmosphere Inspection (Accumulation): Tests gas inside a part where part inside an enclosure, but the enclosure is maintained at near barometric condition. This configuration, although simpler, is ~1000 less sensitive compared to the vacuum inspection.
Micro-Flow vs. Helium Mass Spectrometry (Chamber Test)
|Function||Mass Extraction Technology||Helium Mass Spectrometry|
|Leak Flow Measurement||Direct, accurate and independent of UUT volume||Indirect, required frequent calibration and is volume sensitive|
|Gas Used||Any gas, mostly air or nitrogen||Helium|
|Max. Sensitivity||6×10-7 std. cc/sec.||1×10-10 std. cc/sec.|
|Vacuum Level (absolute pressure) at instrument||1 to 200 mm Hg (1-200 tor)||1×10-3 to 1×10-4 mm Hg (tor)|
|Drive, measurement stability||Very Good (2-3%/year or better); Sensitive to UUT out-gassing||Poor, sensitive to background helium level|
|Vacuum System||Simple mechanical vacuum pump||Sensitive hard vacuum system with diffusion or molecular pumps|
|Operational Cost||Very low||Expensive – helium is an expensive gas, and becomes harder to get.|
|Maintenance Cost||Very low, simple system||Expensive, sensitive pumps and valves|
|Response Time||Slow||Slower at higher sensitivity|
Helium Sniffer Detectors
Helium sniffers only find the point of leak, which are misleading. Helium sniffing is very operator dependent. Helium permeates through Teflon and other seals, creating false indications. Some companies will use these as line leak testers, which is incorrect.
Consult ATC, Inc. if you are looking to upgrade or replace your tracer gas leak test system.